Sequence control over thermo-triggered micellization and smart nanogels of copolymers based on PEGMA and aldehyde-functionalized monomer

Abstract

This paper describes the sequence control over thermo-triggered micellization and the corresponding dynamic nanogels of copolymers of poly[poly(ethylene glycol) methyl ether methacrylate] (PEGMA) and 1,3-(4-formylphenoxy)-2-hydroxypropyl methacrylate (FPHPMA). To this end, the well-defined copolymers in the sequences of P(FPHPMA-ran-PEGMA), P(FPHPMA-ran-PEGMA)-b-PFPHPMA and P(FPHPMA-ran-PEGMA)-b-PPEGMA, at a molar ratio of [FPHPMA]:[PEGMA]≈1:1 and a fixed overall degree of polymerization or DP≈50, were synthesized via reversible addition-fragmentation chain transfer radical polymerization or RAFT polymerization under mild visible light radiation at 25 °C. The results demonstrated that altering the sequence from P(FPHPMA-ran-PEGMA) to P(FPHPMA-ran-PEGMA)-b-PPEGMA or P(FPHPMA-ran-PEGMA)-b-PFPHPMA led to an increase of cloud point and decrease of hydrodynamic diameter from hundreds of nm to tens of nm. Moreover, altering the copolymer sequence resulted in the thermo-triggered micellization mechanism changing from the insertion/expulsion of single chains to fusion/fission of their pre-assembled “polymerases”. The hysteresis and solvent isotopic effects varied with the sequence of copolymers. Moreover, the thermo-induced dehydration and the apparent reactivity of aldehyde functionalities in swollen micelles also varied with the sequence. These thermo-induced micelles could react with diamine to form dynamic nanogels. The pH- and/or thermo-triggered swellability of these nanogels could be adjusted by changing the sequence.